Two inspectors at the federal agency in charge of aviation safety were threatened with dismissal when they pointed out a major U.S. airline’s serious safety violations to agency supervisors who had cozy relationships with the carrier.

Now government whistleblowers, the Federal Aviation Administration inspectors told federal lawmakers this week that supervisors at the agency have for years looked the other way while Southwest Airlines repeatedly violated crucial safety and record-keeping rules that endangered the public.

Testifying before a House Transportation Committee, the aviation safety inspectors—Douglas Peters and Charalambe Bobby Boutris—said that Southwest specifically hired former FAA inspectors as compliance managers because they were tight with the current government inspectors.

As a result the carrier was allowed to slide on numerous crucial inspections involving fuselage cracks that should have been repaired under FAA rules, according to the whistleblowers. The cracks could result in a sudden fracture and failure of the skin panels and fuselage and lead to rapid decompression which would have a catastrophic impact during flight, according to Boutris.

This is hardly the first public betrayal by a troubled agency that for years has been accused by lawmakers of lacking leadership. Late last year, a scathing Congressional report detailed the serious safety mishaps that regularly occur on runways across the country, especially at the nation’s busiest airports.

The report blasted the FAA because the agency has long claimed that pilots and air traffic controllers follow strict federal rules that permit only one plane at a time on or near a runway therefore drastically reducing serious runway incursions. The opposite is true, according to the report, which revealed that such close calls are at an all-time high.

Illustrating the FAA’s dangerously close ties to the industry it regulates, the agency’s chief recently accepted a job as head of a powerful trade group that represents major firms regulated by the FAA. As head of the FAA for five years, Marion Blakey oversaw and awarded lucrative federal contracts to many of the firms that she now represents.